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United States Patent |
5,132,329
|
Lynch
,   et al.
|
July 21, 1992
|
Integral skin polyurethane foam
Abstract
A process for preparing a flexible, low density, integral skin polyurethane
foam wherein water is used as the sole blowing and density controlling
agent. The process entails reacting an isocyanate component with a
compound containing isocyanate reactive groups and further containing
ether linkages, a polyurethane promoting catalyst, an alcohol, a
surfactant, a chain extender and optional additives. The reaction is
carried out at molded densities of from 15 pcf to 30 pcf in molds
preheated to about 90.degree. F. to about 130.degree. F.
Inventors:
|
Lynch; Thomas M. (Southgate, MI);
Harrison; Richard P. (Lincoln Park, MI)
|
Assignee:
|
BASF Corporation (Parsippany, NJ)
|
Appl. No.:
|
585446 |
Filed:
|
September 20, 1990 |
Current U.S. Class: |
521/51; 264/51 |
Intern'l Class: |
C08G 018/14 |
Field of Search: |
521/51
264/51
|
References Cited
U.S. Patent Documents
4605681 | Aug., 1986 | Grey et al. | 521/51.
|
4780482 | Oct., 1988 | Kruger | 521/51.
|
Primary Examiner: Welsh; Maurice J.
Attorney, Agent or Firm: Connaughton; Martin P.
Parent Case Text
This is a continuation-in-part of copending U.S. application Ser. No.
07/504,813, filed Apr. 5, 1990 & now abandoned.
Claims
We claim:
1. A process for preparing a flexible, low density, integral skin foam,
free of chlorofluorocarbon blowing agents, comprising reacting:
A) an isocyanate component in which all of the isocyanate groups are
aromatically bound; with
B) compounds bearing hydrogen atoms reactive with isocyanate groups and
having ether linkages, molecular weights from about 2500 to about 6000 and
an average functionality of at least 1.5;
C) water as a blowing agent present in an amount up to 1.0 pbw based on the
total weight of all nonisocyanate components;
D) an effective amount of a polyurethane promoting catalyst;
E) a monofunctional alcohol having from about 10 to about 20 carbons;
F) a surfactant; and
G) a chain extender;
wherein molded densities are from about 15 pcf to about 30 pcf and gel time
is from about 5 seconds to about 20 seconds faster than the total rise
time.
2. A process as claimed in claim 1, wherein the isocyanate component is a
polymethylene polyphenylisocyanate, a urethane modified diphenylmethane
diisocyanate prepolymer, a carbodiimide modified 4,4'-diphenylmethane
diisocyanate, or a mixture thereof.
3. A process as claimed in claim 1, wherein the isocyanate component and
the mixture of nonisocyanate components are present in a ratio of from
about 44/100 to about 57/100 pbw isocyanate/nonisocyanate.
4. A process as claimed in claim 1, wherein the compound bearing active
hydrogens (B) is a polyether copolymer having a molecular weight of from
4000 to 5000 and an average functionality of about 1.75 to about 3.0, an
acrylonitrile-styrene graft polyether copolymer, or mixtures thereof and
is present in amounts from 85.0 pbw to about 93.0 pbw based on the total
weight of nonisocyanate components.
5. A process as claimed in claim 1, wherein water (C) is present in amounts
from about 0.4 pbw to about 0.8 pbw based on the total weight of
nonisocyanate components.
6. A process as claimed in claim 1, wherein the polyurethane promoting
catalyst (D) is a tertiary amine, organotin compound, or mixtures thereof
present in amounts of from about 0.5 pbw to about 1.6 pbw based on the
total weight of nonisocyanate components.
7. A process as claimed in claim 1, wherein the monofunctional alcohol (E)
is a mixture of monofunctional alcohols having from 12 to 15 carbons and
is present in amounts from about 0.4 pbw to about 1.0 pbw based on the
total weight of nonisocyanate components.
8. A process as claimed in claim 1, wherein the surfactant (F) is a
silicone containing polyether, an ester, or mixtures thereof, present in
amounts of from about 0.3 pbw to 0.6 pbw based on the total weight of all
nonisocyanate components.
9. A process as claimed in claim 1, wherein the chain extender (G) is
ethylene glycol, diethylene glycol or mixtures thereof present in amounts
of from 5.0 pbw to about 6.5 pbw based on the total weight of
nonisocyanate components.
10. A process as claimed in claim 1, further comprising an additive present
in amounts up to about 5 pbw of the total weight of all nonisocyanate
components.
11. A process as claimed in claim 1, wherein the molded density is from 18
pcf to about 25 pcf.
12. A process according to claim 1, wherein the reaction is carried out in
a mold preheated to 90.degree. to 130.degree. F.
13. A process as claimed in claim 1, further comprising an additive present
in amounts up to about 5 pbw of the total weight of all isocyanate
components.
14. A process as claimed in claims 10 or 13, wherein the additive is gamma
butyrolactone.
15. A process as claimed in claim 1, wherein the isocyanate component and
nonisocyanate components are injected into a closed mold using a high
pressure injection technique.
16. A process as claimed in claim 1, wherein the isocyanate component and
nonisocyanate components are poured into a preheated open mold.
17. A flexible, low density, integral skin polyurethane foam containing no
chlorofluorocarbons or volatile organic alkanes as blowing agents,
consisting essentially of the reaction product of:
A) an isocyanate component in which all of the isocyanate groups are
aromatically bound;
B) a polyether copolymer or mixture of polyether copolymers bearing
hydrogen atoms reactive with isocyanate groups and having molecular
weights from 2500 to about 6000 and an average functionality of at least
1.5;
C) water as the exclusive blowing agent present in amounts up to 1.0 pbw
based on the total weight of nonioscyanate components;
D) an effective amount of a polyurethane promoting catalyst;
E) a monofunctional alcohol having from about 10 to about 20 carbons;
F) a surfactant;
G) a chain extender selected from the group consisting of ethylene glycol,
diethylene glycol, and mixtures thereof;
wherein the flexible integral skin foam has a molded density of about 15
pcf to about 30 pcf.
Description
BACKGROUND OF THE INVENTION
The present invention pertains to a process for preparing integral skin
polyurethane foam. In particular the invention relates to a process for
preparing an integral skin foam wherein water is the main blowing and
density controlling agent. The use of water as the blowing agent obviates
the need to use chlorofluorocarbons which have been shown to be of
detriment to the environment. Although the products of this process may
exhibit a wide range of densities and hardness'; it is those products
referred to as low density, flexible, integral skin foams that are of
particular interest.
DESCRIPTION OF THE RELATED ART
Integral skin foams are well known to those skilled in the art of
polyurethane foams. Such foams have a cellular interior and a higher
density microcellular or noncellular skin. In general, to prepare such
foams one reacts an organic isocyanate with a substance having at least
one isocyanate reactive group, in the presence of a catalyst, blowing
agent, and a variety of optional additives. The reaction is carried out in
a mold where a higher density skin forms at the interface of the reaction
mixture and the inner surface of the mold.
At the present time, the most common type of blowing agent used in integral
skin polyurethane foams is chlorofluorocarbons (CFC) or combinations of
CFC's and other blowing agents. Industry today, however, is faced with a
mandate to reduce and eventually eliminate the use of CFC's. To this end
much energy is being devoted.
Past methods of preparing integral skin polyurethanes with CFC's as a
blowing agent include the following. G.B. Pat. No. 1,209,297 teaches the
use of a combination blowing agent consisting of a CFC and hydrate of an
organic compound which splits off water at temperatures above 40.degree.
C. This blowing agent or combination of agents was used in a formulation
with a suitable polyisocyanate a polyol containing hydroxyl groups and a
catalyst. This patent discloses the undesirability of having free water in
the system. The patent states that the presence of even small quantities
of water produce a skin which is permeated with fine cells.
U.S. Pat. No. 4,305,991 describes a process for preparing integral skin
polyurethane foams wherein a polyisocyanate, containing aliphatically
and/or cycloaliphatically bound isocyanate groups, is reacted with
polyhydroxyl compounds containing ether linkages, a chain extender, a
catalyst, additives and a blowing agent. The blowing agent is
characterized as a readily volatile organic substance. Examples of which
include both halogenated and nonhalogenated volatile organic compounds, to
which water may be added as a chemical blowing agent.
More recently attempts have been made to evaluate the performance of
alternate blowing agents to CFC's. In a paper by J. L. R. Clatty and S. J.
Harasin, entitled, Performance of Alternate Blowing Agents to
Chlorofluorocarbons in RIM Structural and Elastomeric Polyurethane Foams,
presented to the 32nd Annual Polyurethane Technical/Marketing Conference,
October, 1989, the authors addressed the use of water as a blowing agent
for integral skin polyurethane reaction injection molded systems (RIM). In
this application the water concentration in the system is controlled by
the concentration and type of molecular sieves used. As in the Great
Britain patent discussed previously the water is not in a free form but
bound in some manner. In this instance, the authors state that this
process is limited to use in rigid foam systems and the flexible integral
skin formulations may best be served by using HCFC's or HCFC-22 as
substitutes for CFC's.
Summary of the Invention
Prior processes have used water in combination with other blowing and
density controlling agents as a means of preparing integral skin
polyurethane foams.
It is the object of the present invention to provide a flexible, low
density integral skin polyurethane foam and a process wherein the integral
skin polyurethane foam uses no CFC's or volatile alkane blowing agent. The
process for said invention comprises reacting:
A) a polyisocyanate component;
B) compounds bearing hydrogen atoms reactive with isocyanate groups and
having an average functionality of at least 1.5 and further containing
ether linkages;
C) water;
D) an effective amount of a polyurethane promoting catalyst;
E) an alcohol having from 10 to about 20 carbons;
F) a surfactant; and
G) a chain extender.
optional additives may be added.
DETAILED DESCRIPTION OF THE INVENTION
The instant invention relates to a process for the production of integral
skin polyurethane foams and more particularly those integral skin foams
which are flexible and have a molded density of from about 15 pcf to about
30 pcf. In general, potential applications for this material include but
are not limited to automotive parts such as steering wheels, armrests,
horn covers, headrests, or trim and non-automotive applications not
limited to, shoe soles, gaskets, or furniture parts.
The process comprises reacting a polyisocyanate component in which all of
the isocyanate groups are aromatically bound; with a polyether having a
molecular weight from about 2500 to about 6000; water used as the
exclusive blowing agent; a catalyst of a type known by those skilled in
the art, in sufficient quantity to catalyze the reaction; an alcohol
having from about 10 to 20 carbons; a surfactant such as those silicone
containing compounds known as "Superwetting Agents" made by the Dow
Corning Corporation, and a chain extender such as ethylene glycol or
diethylene glycol.
The organic polyisocyanates used in the instant process contain
aromatically bound isocyanate groups. Representatives of the types of
organic polyisocyanates contemplated herein include, for example,
1,4-diisocyanatobenzene, 1,3-diisocyanato-o-xylene,
1,3-diiocyanato-p-xylene, 1,3-diisocyanato-m-xylene,
2,4-diisocyanato-1-chlorobenzene, 2,4-diisocyanato-l-nitrobenzene,
2,5-diisocyanato-l-nitrobenzene, m-phenylene diisocyanate, 2,4-toluene
diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2-6 toluene
diisocyanate, hexahydrotoluene diisocyanate, 1,5-naphthylene diisocyanate,
1-methoxy-2,4-phenylene diisocyanate, hexahydrotoluene diisocyanate,
1,5-naphthylene diisocyanate, 1-methoxy-2,4-phenylene diisocyanate,
4,4'-diphenylmethane diisocyanate, 4,4'-biphenylene diisocyanate,
3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3'-4,4'-diphenylmethane
diisocyanate and 3,3'-dimethyldiphenylmethane-4,4'-diisocyante; the
triisocyanates such as 4,4',4"-triphenylmethane triisocyanate,
polymethylene polyphenylene polyisocyanate and 2,4,6-toluene
triisocyanate; and the tetraisocyanates such as
4,4-dimethyl-2,2'-5,5'-diphenylmethane tetraisocyanate. Especially useful
due to their availability and properties are 2,4'-diphenylmethane
diisocyanate, 4,4-diphenylmethane diisocyanate, polymethylene
polyphenylene polyisocyanate, and mixtures thereof.
These polyisocyanates are prepared by conventional methods known in the art
such as the phosgenation of the corresponding organic amine. Included
within the useable isocyanates are the modifications of the above
isocyanates which contain carbodiimide, allophonate, urethane or
isocyanurate structures. Generally, these modified isocyanates will have
an isocyanate content of from about 20 percent to about 40 percent by
weight.
Mixtures of polymeric diphenylmethane diisocyanate (poly MDI) and
carbodiimide or urethane modified MDI are preferred. The above mentioned
polymeric diphenylmethane diisocyante compounds are marketed by BASF under
the trademark designation LUPRANATE.TM. M-20. M-20 has an average
functionality of about 2.7 and an isocyanate content of about 31% by
weight, and is represented by the general formula:
##STR1##
where n is greater than 1.
Carbodiimide modified diphenylmethane diisocyanates are well known to those
skilled in the art, and are prepared by catalytic dimerization of MDI.
Such a carbodiimide modified diisocyanate is marketed by BASF under the
trademark designation LUPRANATE.TM. MM-103. MM-103 has an isocyanate
content of about 29% by weight, and is represented by the formula:
##STR2##
Suitable urethane modified diisocyantes are represented by the general
formula:
##STR3##
compound having a functionality greater than one; preferably having a
functionality of two. Examples of these compounds include; ethylene
glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycol
initiated polyoxyalkylene polymers and copolymers, and mixtures thereof.
An example of such a urethane modified diisocyanate is marketed by BASF
under the trademark designation LUPRANATE.TM. MP-102. MP-102 is a pure MDI
prepolymer with an isocyanate content of about 23% by weight. These
compounds and their methods of preparation are well known in the art.
Any suitable polyoxyalkylene polyether polyol may be used such as those
resulting from the polymerization of a polyhydric alcohol and an alkylene
oxide. Representatives of such alcohols may include, ethylene glycol,
propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol,
1,4-butanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol,
1,6-hexanediol, 1,7-heptanediol, glycerol, 1,1,1-trimethylolpropane,
1,1,1-trimethylolethane, or 1,2,6-hexanetriol. Any suitable alkylene oxide
may be used such as ethylene oxide, propylene oxide, butylene oxide,
amylene oxide, and mixtures of these oxides. The polyalkylene polyether
polyols may be prepared from other starting materials such as
tetrahydrofuran and alkylene oxide-tetrahydrofuran mixtures;
epihalohydrins such as epichlorohydrin; as well as aralkylene oxides such
as styrene oxide. The polyoxyalkylene polyether polyols may have either
primary or secondary hydroxyl groups. Included among the polyether polyols
are polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene
glycol, polytetramethylene glycol, block copolymers, for example,
combinations of polyoxypropylene and polyoxyethylene glycols,
poly-1,2-oxybutylene and polyoxyethylene glycols and copolymer glycols
prepared from blends or sequential addition of two or more alkylene
oxides. The polyoxyalkylene polyether polyols may be prepared by any known
process such as, for example, the process disclosed by Wurtz in 1859 and
Encyclopedia of Chemical Technology, Vol. 7, pp 257-262, published by
Interscience Publishers, Inc. (1951) or in U.S. Pat. No. 1,922,459.
Other polyoxyalkylene polyether polyols which may be employed are those
which contain grafted therein vinylic monomers.
The polyols which have incorporated therein the vinylic polymers may be
prepared (1) by the in situ free-radical polymerization of an
ethylenically unsaturated monomer or mixture of monomers in a polyol, or
(2) by dispersion in a polyol of a preformed graft polymer prepared by
free-radical polymerization in a solvent such as described in U.S. Pat.
Nos. 3,931,092, 4,014,846, 4,093,573, and 4,122,056, the disclosures of
which are herein incorporated by reference, or (3) by low temperature
polymerization in the presence in the presence of chain transfer agents.
These polymerizations may be carried out at a temperature between
65.degree. C. and 170.degree. C., preferably between 75.degree. C. and
135.degree. C.
The amount of ethylenically unsaturated monomer employed in the
polymerization reaction is generally from one percent to 60 percent,
preferably from 10 percent to 40 percent, based on the total weight of the
product. The polymerization occurs at a temperature between about
80.degree. C. and 170.degree. C., preferably from 75.degree. C. to
135.degree. C.
The polyols which may be employed in the preparation of the graft polymer
dispersions are well known in the art. Both conventional polyols
essentially free from ethylenic unsaturation such as those described in
U.S. Pat. No. Re. 28,715 and unsaturated polyols such as those described
in U.S. Pat. Nos. 3,652,659 and Re. 29,014 may be employed in preparing
the graft polymer dispersions used in the instant invention, the
disclosures of which are incorporated by reference. Representative polyols
essentially free from ethylenic unsaturation which may be employed are
well known in the art. They are often prepared by the catalytic
condensation of an alkylene oxide or mixture of alkylene oxides either
simultaneously or sequentially with an organic compound having at least
two active hydrogen atoms such as evidenced by U.S. Pat. Nos. 1,922,459;
3,190,927, and 3,346,557, the disclosures of which are incorporated by
reference.
The unsaturated polyols which may be employed for preparation of graft
copolymer dispersions may be prepared by the reaction of any conventional
polyol such as those described above with an organic compound having both
ethylenic unsaturation and a hydroxyl, carboxyl, anhydride, isocyanate or
epoxy group or they may be prepared by employing an organic compound
having both ethylenic unsaturation an a hydroxyl, carboxyl, anhydride, or
epoxy group as a reactant in the preparation of the conventional polyol.
Representative of such organic compounds include unsaturated mono and
polycarboxylic acids and anhydrides such as maleic acid and anhydride,
fumaric acid, crotonic acid and anhydride, propenyl succinic anhydride,
and halogenated maleic acids and anhydrides, unsaturated polyhydric
alcohols such as 2-butene-1,4-diol, glycerol allyl ether,
trimethylolpropane allyl ether, pentaerythritol allyl ether,
trimethylolpropane allyl ether, pentaerythritol allyl ether,
pentaerythritol vinyl ether, pentaerythritol diallyl ether, and
1-butene-3,4-diol, unsaturated epoxides such as 1-vinylcyclohexene
monoxide, butadiene monoxide, vinyl glycidyl ether, glycidyl methacrylate
and 3-allyloxypropylene oxide.
As mentioned above, the graft polymer dispersions used in the invention are
prepared by the in situ polymerization of an ethylenically unsaturated
monomer or a mixture of ethylenically unsaturated monomers, either in a
solvent or in the above-described polyols. Representative ethylenically
unsaturated monomers which may be employed in the present invention
include butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene,
styrene, a-methylstyrene, methylstyrene, 2,4-dimethylstyrene,
ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene,
cyclohexylstyrene, benzylstyrene, and the like; substituted styrenes such
as chlorostyrene, 2,5-dichlorostyrene, bromostyrene, fluorostyrene,
trifluoromethylstyrene, iodostyrene, cyanostyrene, nitrostyrene,
N,N-dimethylaminostyrene, acetoxystyrene, methyl-4-vinylbenzoate,
phenoxystyrene, p-vinyldiphenyl sulfide, p-vinylphenyl phenyl oxide, and
the like; the acrylic and substituted acrylic monomers such as
acrylonitrile, acrylic acid, methacrylic acid, methylacrylate,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate,
cyclohexyl methacrylate, benzyl methacrylate, isopropyl methacrylate,
octyl methacrylate, methacrylonitrile, methyl a-chloroacrylate, ethyl
a-ethoxyacrylate, methyl a-acetam; inoacrylate, butyl acrylate,
2-ethylhexyl acrylate, phenyl acrylate, phenyl methacrylate,
a-chloroacrylonitrile, methacrylonitrile, N,N-dimethylacrylamide,
N,N-dibenzylacrylamide, N-butylacrylamide, N,N-dibenzylacrylamide,
N-butylacrylamide, methacryl formamide, and the like; the vinyl esters,
vinyl ethers, vinyl ketones, etc., such as vinyl acetate, vinyl
chloroacetate, vinyl alcohol, vinyl butyrate, isopropenyl acetate, vinyl
formate, vinyl acrylate, vinyl methacrylate, vinyl methoxyacetate, vinyl
benzoate, vinyl iodide, vinyltoluene, vinylnaphthalene, vinyl bromide,
vinyl fluoride, vinylidene bromide, 1-chloro-1-fluoroethylene, vinylidene
fluoride, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl
butyl ether, vinyl 2-ethylhexyl ether, vinyl phenyl ether, vinyl
2-butoxyethyl ether, 2,4-dihydro-1,2-pyran, 2-butoxy-2'-vinyloxy diethyl
ether, vinyl 2-ethylthioethyl ether, vinyl methyl ketone, vinyl ethyl
ketone, vinyl phenyl ketone, vinyl phosphonates such as bis(b-chloroethyl)
vinyl phosphonate, vinyl ethyl sulfide, vinyl ethyl sulfone,
N-methyl-N-vinyl acetamide, N-vinylpyrrolidone, vinyl imidazole, divinyl
sulfide, divinyl sulfoxide, divinyl sulfone, sodium vinylsulfonate, methyl
vinylsulfonate, N-vinyl pyrrole, and the like; dimethyl fumarate, dimethyl
maleate, maleic acid, crotonic acid, fumaric acid, itaconic acid,
monomethyl itaconate, butylaminoethyl methacrylate, dimethylaminoethyl
methacrylate, glycidyl acrylate, allyl alcohol, glycol monoesters of
itaconic acid, dichlorobutadiene, vinyl pyridine, and the like. Any of the
known polymerizable monomers can be used and the compounds listed above
are illustrative and not restrictive of the monomers suitable for us in
this invention. Preferably, the monomer is selected from the group
consisting of acrylonitrile, styrene, methyl methacrylate and mixtures
thereof.
Illustrative initiators which may be employed for the polymerization of
vinyl monomers are the well-known free radical types of inyl
polymerization initiators, for example, the peroxides, persulfates,
perborates, percarbonates, azo compounds, etc., including hydrogen
peroxide, dibenzoyl peroxide, acetyl peroxide, benzoyl hydroperoxide,
t-butyl hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, butyryl
peroxide, diisopropylbenzene hydroperoxide, cumeme hydroperoxide,
paramenthane hydroperoxide, di-a-cumyl peroxide, dipropyl peroxide,
diisopropyl peroxide, difuroyl peroxide, ditriphenylmethyl peroxide,
bis(p-methoxybenzoyl) peroxide, p-monoethoxybenzoyl peroxide, rubene
peroxide, ascaridol, t-butyl peroxybenzoate, diethyl peroxyterephthalate,
propyl hydroperoxide, isopropyl hydroperoxide, n-butyl hydroperoxide,
t-butyl hydroperoxide, cyclohexyl hydroperoxide, trans-decalin
hydroperoxide, amethylbenzyl hydroperoxide, a-methyl-a-ethyl benzyl
hydroperoxide, tetralin hydroperoxide, triphenylmethyl hydroperoxide,
diphenylmethyl hydroperoxide, a-a'-azo-bis(2-methyl) butyronitrile,
a,a'-azo-bis(2-methyl) heptonitrile, 1,1-azo-bis (1-cyclohexane)
carbonitrile, dimethyl a,a'-azobis(isobutyronitrile),
4,4'-azo-bis(4-cyanopetanoic) acid, azo-bis(isobutyronitrile),
1-t-amylazo-1-cyanocyclohexane,
2-t-butylazo-2-cyano-4-methoxy-4-methylpentane,
2-t-butylazo-2-cyano-4-methylpentane, 2-(t-butylazo)isobutyronitrile,
2-t-butylazo-2-cyanobutane, 1-cyano-1-(t-butylazo)cyclohexane, t-butyl
peroxy-2-ethylhexanoate, t-butylperpivalate,
2,5-dimethyl-hexane-2,5-diper-2-ethyl hexoate, t-butylperneo-decanoate,
t-butylperbenzoate, t-butyl percrotonate, persuccinic acid, diisopropyl
peroxydicarbonate, and the like; a mixture of initiators may also be used.
Photochemically sensitive radical generators may also be employed.
Generally from about 0.5 percent to about 10 percent, preferably from
about 1 percent to about 4 percent, by weight of initiator based on the
weight of the monomer will be employed in the final polymerization.
Stabilizers may be employed during the process of making the graft polymer
dispersions. One such example is the stabilizer disclosed in U.S. Pat. No.
4,148,840 which comprises a copolymer having a first portion composed of
an ethylenically unsaturated monomer or mixture of such monomers and a
second portion which is a propylene oxide polymer. Other stabilizers which
may be employed are the alkylene oxide adducts of copolymers of
styrene-allyl alcohol.
The preferred polyols are polyethers having an average functionality of
about 1.75 to about 3.0 and a molecular weight range of from about 4000 to
about 5000. The most preferred polyols are polyethers which are copolymers
of ethylene oxide and propylene oxide having a diol or triol initiator
such as propylene glycol or glycerine.
Any suitable catalyst may be used including tertiary amines such as,
triethylenediamine, N-methylmorpholine, N-ethylmorpholine,
diethylethanolamine, N-cocomorpholine,
1-methyl-4-dimethylaminoethylpiperazine, methoxypropyldimethylamine,
N,N,N'-trimethylisopropyl propylenediamine,
3-diethylaminopropyldiethylamine, dimethylbenzylamine, and the like.
Examples of such commercially available catalysts is the DABCO.RTM. series
available through Air Products, Corp. Other suitable catalysts are, for
example, dibutyltin dilaurate, dibutyltindiacetate, stannous chloride,
dibutyltin di-2-ethyl hexanoate, stannous oxide, available under the
FOMREZ.RTM. trademark, as well as other organometallic compounds such as
are disclosed in U.S. Pat. No. 2,846,408.
An alcohol having from about 10 to about 20 carbons or mixtures thereof, is
used according to the present invention. Alcohols of this type are known
to those skilled in the art. The types of alcohols contemplated are
commonly produced via the oxo process and are referred to as oxo-alcohols.
Examples of some commercially available products include LIAL 125 from
Chimica Augusta SpA or NEODOL.RTM. 25 produced by Shell.
A surface active agent is necessary for production of integral skin
polyurethane foam according to the present invention. Surfactants which
may be used are those which aid in homogenizing the initial materials and
may also be suitable for regulating cell structure. Typical examples are
foam stabilizers such as siloxane oxyalkylene heterol polymers and other
organic polysiloxanes, oxyethylated alkyl phenol, oxyethylated fatty
alcohols, paraffin oils, castor oil ester, phthalic acid esters,
ricindolic acid ester, and Turkey red oil, as well as cell regulators such
as paraffins.
Chain extending agents employed in the preparation of integral skin
polyurethane foams include those having two functional groups bearing
active hydrogen atoms. A preferred group of chain extending agents
includes ethylene glycol, diethylene glycol, propylene glycol or
1,4-butanediol.
Additives which may be used in the process of the present invention include
known pigments, such as carbon black, dyes and flame retarding agents
(e.g., tris-chloroethyl phosphates or ammonium phosphate and
polyphosphate), stabilizers against ageing and weathering, plasticizers,
such as gamma butyrolactone; fungistatic and bacteriostatic substances,
and fillers.
The main blowing and density controlling agent used according to the
present invention is water. For the purpose of the invention water is
present in amounts up to and including 1.0 pbw based on the total weight
of the nonisocyanate components. It is preferably present in amounts from
about 0.4 pbw to 1.0 pbw based on the total of the nonisocyanate
components.
The mechanical parameters of the instant process are flexible and depend on
the final application of the integral skin polyurethane foam. The reaction
system is versatile enough that it may be made in a variety of densities
and hardness'. However, the reactivity profile of the system is important.
The system should have a gel time from about 5 seconds to about 20 seconds
faster than the total rise time. The system may be introduced into a mold
in a variety of ways known to those skilled in the art. It may be shot
into a preheated closed mold via high pressure injection technique. In
this manner it processes well enough to fill complex molds at low mold
densities (from 18 pcf to 25 pcf). It may also be run using a conventional
open mold technique wherein the reaction mixture or system is poured or
injected at low pressure or atmospheric pressure into a preheated open
mold. In the instant process the system may be run at mold temperatures
from about 85.degree. F. to about 120.degree. F. with from about
90.degree. F. to about 110.degree. F. being preferred.
Having thus described the invention, the following examples are given by
way of illustration.
TEST METHODS
Density ASTM D-1622
Tensile Elongation ASTM D412 Die A
Split Tear ASTM D-1938
Graves Tear ASTM D-412 Die C
Shore Hardness ASTM D-2240
Compression Set ASTM D-3574.
EXAMPLE 1
86.33 parts by weight (pbw) of a polyether component comprising, 78.33 pbw
of a glycerine initiated polyoxypropylene-polyoxyethylene copolymer having
a hydroxyl number of 35 and 8.0 pbw of an acrylonitrile-styrene graft,
trimethylolpropane initiated polyoxypropylene-polyoxyethylene copolymer
having a hydroxyl of 24, was combined with 6.00 pbw ethylene glycol, 0.75
pbw water, 0.70 pbw of a C.sub.12 -C.sub.15 oxoalcohol, 0.60 pbw of a
dialkyl phthalate surfactant, 5.00 pbw of gamma butyrolactone, and 0.62
pbw of a catalyst mixture consisting of 0.51 pbw of an amine catalyst in
dipropylene glycol, 0.02 pbw of a dibutyltin dilaurate catalyst and 0.09
pbw of an acid blocked amine catalyst in dipropylene glycol.
This polyol resin component was combined with an isocyanate blend in a
ratio of 100/57.8, polyol/isocyanate. The isocyanate is a 73/22/5 blend of
a urethane modified pure diphenylmethane diisocyanate prepolymer,
polymethylene polyphenylisocyante and a carbodiimide modified
4,4'-diphenylmethane diisocyanate, such as LUPRANATE.TM. M-20,
LUPRANATE.TM. MP-102 and LUPRANATE.TM. MM-103.
The room temperature polyol/isocyanate mixture was poured into an open mold
preheated to 90.degree.-110.degree. F. The mold was subsequently closed.
Two molded parts were made having excellent skin formation and the
following mechanical properties:
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1 2
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Density (pcf)
core 26.35 25.61
section 27.78 27.51
Split Tear (pi)
skin 23.9 23.3
skin and core 20.2 21.7
core 10.9 13.0
Graves Tear (pi)
skin 73.0 73.8
skin and core 52.4 52.6
core 29.4 31.2
Compression Set (% set)
50% @ 158.degree. F. 13.30 13.41
75% @ 158.degree. F. 11.11 12.12
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EXAMPLE 2
91.0 pbw of a glycerine initiated polyoxypropylene-polyoxyethylene
copolymer which had a hydroxyl number of 27.5 was combined with 6.0 pbw
ethylene glycol, 0.7 pbw water, 0.6 pbw of a C.sub.12 -C.sub.15
oxoalcohol, 0.5 pbw of a surfactant comprised of
methyl(polyethyleneoxide)-bis(trimethylsiloxy) silane and polyethylene
oxide monoallyl ether, and 1.2 pbw of an amine catalyst. 1.0 pbw based on
the total weight of the polyol resin of carbon black was added.
The polyol resin component was combined with an isocyanate blend in a ratio
of 100/55.1, polyol/isocyanate. The isocyanate is a 50/50 blend of a
carbodiimide modified 4,4'-diphenylmethane diisocyanate and a urethane
modified diphenylmethane diisocyanate prepolymer, such as LUPRANATE.TM.
MM-103 and LUPRANATE.TM. MP-102.
The room temperature polyol/isocyanate mixture was poured into an open mold
preheated to 95.degree.-100.degree. F. The mold was subsequently closed.
Two molded parts were made having a clearly defined skin. The surfaces of
the molded parts were wiped with methylene chloride and isopropyl alcohol.
There was no detectable effect. The molded parts exhibited the following
mechanical properties.
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1 2
______________________________________
Density (pcf)
section 21.2 23.7
Split Tear (pi)
skin 53.6 56.5
skin and core 27.6 26.6
core 11.0 11.6
Graves Tear (pi)
skin 53.6 56.5
skin and core 52.7 58.5
core 27.1 30.4
Shore "A" hardness (5 sec)
56 60
Tensile Strength (psi)
skin 313.4 346.3
skin and core 305.1 357.1
core 190.1 202
Elongation, % break
skin 186.7 178.0
skin and core 176.7 173.3
core 158.3 128.0
Compression Set (% set)
50% @ 72.degree. F. 19.65 17.89
25% @ 72.degree. F. 10.74 13.33
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EXAMPLE 3
92.815 pbw of a polyether component comprising; 77.815 pbw of a glycerine
initiated polyoxypropylene polyoxyethylene copolymer having a hydroxyl
number of 27.5 and 15.0 pbw of an acrylonitrile-styrene graft,
trimethylolpropane initiated polyoxypropylene-polyoxyethylene copolymer
having a hydroxyl number of 24, was combined with 4.7 pbw ethylene glycol,
0.7 pbw of a C.sub.12 -C.sub.15 oxoalcohol, 0.50 pbw of a surfactant
comprised of methyl (polyethylene oxide)-bis(trimethylsiloxy) silane and
polyethylene oxide monoallyl ether, 0.50 pbw of a mixture of amine
catalysts and 0.035 pbw of a dibutyltin dilaurate cataylst.
This polyol resin component was combined with an isocyanate blend in a
ratio of 100/46.1, polyol/isocyanate. The isocyanate is a 50/50 blend of a
carbodiimide modified 4,4'-diphenylmethane diisocyanate and a urethane
modified diphenylmethane diisocyanate prepolymer, such as LUPRANATE.TM.
MM-103 and LUPRANATE.TM. MP-102. The room temperature polyol/isocyanate
mixture was poured into an open mold, preheated to 95.degree.-100.degree.
C. and the mold subsequently closed. Two molded parts were made having a
clearly defined skin and the following mechanical properties:
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1 2
______________________________________
Density (pcf)
section 23.70 27.72
core 20.34 23.88
Tensile Strength (psi)
skin 420.33 496.33
skin and core 250.00 389.33
core 158.67 229.33
Elongation, % Break
skin 233.33 218.33
skin and core 208.33 206.67
core 210.0 208.33
Split Tear (pi)
skin 13.95 21.30
skin and core 14.85 22.30
core 11.20 13.70
Graves Tear (pi)
skin 68.75 80.35
skin and core 45.35 59.65
core 27.25 36.55
Compression Set (% set)
25% @ 158.degree. F.
100.48 88.14
50% @ 158.degree. F.
64.49 64.25
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EXAMPLE 4
Same as example 3 with the exception of the isocyanate component. A 70/30
blend of a urethane modified diphenylmethane diisocyanate prepolymer and a
polymethylene polyphenylisocyante composition, such as LUPRANATE.TM.
MP-102 and LUPRANATE.TM. M-20 is substituted for the isocyanate in Example
3. The ratio used is 100/47.3, polyol/isocyanate. A molded part was made
having excellent skin formation and the following mechanical properties.
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1
______________________________________
Density (pcf)
section 27.01
core 23.92
Tensile Strength (psi)
skin 360.33
skin and core 310.33
core 194.00
Elongation, % Break
skin 143.33
skin and core 128.33
core 136.67
Split Tear (pi)
skin 13.75
skin and core 17.40
core 11.80
Graves Tear (pi)
skin 53.95
skin and core 43.75
core 24.80
Compression Set (% set)
50% @ 158.degree. F.
12.88
25% @ 158.degree. F.
32.03
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COMPARATIVE EXAMPLE 1
Same as Example 3 with the exception; no surfactant or oxoalchol is added
to the polyol resin component.
RESULTS
Several molded parts were made having densities ranging from 17 pcf to 25
pcf. A skin was formed but there were numerous air bubbles present. The
skin was also porous.
COMPARATIVE EXAMPLE 2
Freon Blown Integral Skin
83 pbw of a polyol comprising of a trimethylopropane initiated polyether
polyol having a hydroxyl number of 35, trimethylopropane initiated
polyether having a hydroxyl number of 25, and an acrylonitrile-styrene
graft, of a trimethylolpropane initiated polyether having a hydroxyl of 24
is mixed with 1.4 pbw of a tertiary amine catalyst mixture, 6 pbw of a
diol-triol mixture, 0.1 pbw of a silicone containing surfactant and 9.5
pbw Freon F-11A.
This polyol resin was combined with an isocyanate blend in a ratio of
100/46.8, polyol/isocyanate. The isocyanate is a 75/15/5/5 blend of
diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, an
urethane modified diphenylmethane diisocyanate prepolymer and Freon F-113A
an example of such a blend of isocyanates is LUPRANATE.TM. M,
LUPRANATE.TM. M-20, and LUPRANATE.TM. MP-102.
The product was injected into a preheated mold. The molded part exhibits
the following mechanical properties.
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1
______________________________________
Density (pcf)
section 29.3
core 24.9
Shore A Hardness (5 sec.)
69.3
Tensile (psi)
skin 856.7
skin and core 510.0
core 219.0
Split Tear (pi)
skin 27.0
skin and core 19.3
core 8.3
Graves Tear (pi)
skin 99.3
skin and core 52.7
core 22.5
Compression Set (% set)
50% @ 72.degree. F. 19.0
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